#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

int main()
{
	int flag = 1, i = 0;
	double  sum = 0.0;
	for (i = 1; i <= 100; i++)
	{
		sum += (flag * 1.0 / i);
		flag = -flag;
	}
	printf("%lf\n", sum);
	return 0;
}
